<div class="refentry"><a id="glGetUniformBlockIndex"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glGetUniformBlockIndex — retrieve the index of a named uniform block</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">GLuint <strong class="fsfunc">glGetUniformBlockIndex</strong>(</code></td><td>GLuint <var class="pdparam">program</var>, </td></tr><tr><td> </td><td>const GLchar *<var class="pdparam">uniformBlockName</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>program</code></em></span></dt><dd><p>
                    Specifies the name of a program containing the uniform block.
                </p></dd><dt><span class="term"><em class="parameter"><code>uniformBlockName</code></em></span></dt><dd><p>
                    Specifies the address an array of characters to containing the name of the uniform block whose index to retrieve.
                </p></dd></dl></div></div><div class="refsect1"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glGetUniformBlockIndex</code> retrieves the index of a uniform block within <em class="parameter"><code>program</code></em>.
        </p><p>
            <em class="parameter"><code>program</code></em> must be the name of a program object for which the command
            <a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a> must have been called in the past, although it is not required that
            <a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a> must have succeeded. The link could have failed because the number
            of active uniforms exceeded the limit.
        </p><p>
            <em class="parameter"><code>uniformBlockName</code></em> must contain a nul-terminated string specifying the name of the uniform block.
        </p><p>
            <code class="function">glGetUniformBlockIndex</code> returns the uniform block index for the uniform block named <em class="parameter"><code>uniformBlockName</code></em>
            of <em class="parameter"><code>program</code></em>. If <em class="parameter"><code>uniformBlockName</code></em> does not identify an active uniform block of <em class="parameter"><code>program</code></em>,
            <code class="function">glGetUniformBlockIndex</code> returns the special identifier, <code class="constant">GL_INVALID_INDEX</code>. Indices of the active uniform
            blocks of a program are assigned in consecutive order, beginning with zero.
        </p></div><div class="refsect1"><a id="errors"></a><h2>Errors</h2><p>
            <code class="constant">GL_INVALID_OPERATION</code> is generated if <em class="parameter"><code>program</code></em> is not the name of a program object for which
            <a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a> has been called in the past.
        </p></div><div class="refsect1"><a id="notes"></a><h2>Notes</h2><p>
            <code class="function">glGetUniformBlockIndex</code> is available only if the GL version is 3.1 or greater.
        </p></div>
        {$pipelinestall}{$examples}
        <div class="refsect1"><a id="seealso"></a><h2>See Also</h2><p>
            <a class="citerefentry" href="glGetActiveUniformBlockName"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniformBlockName</span></span></a>,
            <a class="citerefentry" href="glGetActiveUniformBlock"><span class="citerefentry"><span class="refentrytitle">glGetActiveUniformBlock</span></span></a>,
            <a class="citerefentry" href="glLinkProgram"><span class="citerefentry"><span class="refentrytitle">glLinkProgram</span></span></a>
        </p></div><div class="refsect1"><div id="Copyright"><h2>Copyright</h2><p>
            Copyright © 2010 Khronos Group.
            This material may be distributed subject to the terms and conditions set forth in
            the Open Publication License, v 1.0, 8 June 1999.
            <a class="ulink" href="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.
        </p></div></div></div>
